1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a sealant of an LCD device formed by a liquid crystal dispensing method.
2. Discussion of the Related Art
Among various ultra-thin flat type display devices, which include display screens having a thickness of several centimeters, the liquid crystal display (LCD) device has received great attention because it is suitable for low operation voltage and has low power consumption. These qualities make the LCD device is suitable for a portable applications. LCD devices are widely used in appliances such as notebook computers and monitors, and are employed in environments such as spacecraft and aircraft.
Generally, an LCD device comprises a lower substrate, an upper substrate, and a liquid crystal layer. The lower substrate includes a thin film transistor and a pixel electrode. The upper substrate includes a black matrix layer, a color filter layer, and a common electrode. The liquid crystal layer is formed between the lower substrate and the upper substrate. In operation, the liquid crystal layer is driven by an electric field formed between the pixel electrode and the common electrode. The electric field controls the light transmittance of the driven liquid crystal layer thereby displaying images.
A liquid crystal injection method of the related art for forming the liquid crystal layer of an LCD device uses a pressure differential and capillary phenomenon to form the liquid crystal layer of an LCD device. The related art liquid crystal injection method will be described as follows.
First, lower and upper substrates are manufactured.
Next, a sealant having an inlet is formed on any one of the lower and upper substrates. The sealant bonds the two substrates to each other. After bonding the two substrates to each other, the sealant is hardened forming bonded substrates.
The bonded substrates are positioned in a vacuum chamber, and the vacuum chamber is evacuated to achieve a vacuum state. While the vacuum state is maintained within the chamber, the bonded substrates are dipped into liquid crystal. The vacuum state of the vacuum chamber creates a vacuum state within the bonded substrates. The vacuum state within the bonded substrates causes the liquid crystal to be injected within the bonded substrates through the inlet through capillary phenomenon. As a result, a liquid crystal layer is formed between the two substrates.
However, as the display area of the LCD device increases in size, the liquid crystal injection method requires longer process times to produce the liquid crystal layer, thereby lowering the productivity.
To overcome this problem of the liquid crystal injection method, a liquid crystal dispensing method has been developed. The liquid crystal dispensing method is described with reference to FIGS. 1A, 1B and 1C.
First, as shown in FIG. 1A, a lower substrate 1 and an upper substrate 3 are prepared.
Referring next to FIG. 1B, a sealant 7 having no inlet is formed on the lower substrate 1, and then liquid crystal 5 is dispensed onto the lower substrate 1, thereby forming a liquid crystal layer.
As shown in FIG. 1C, after bonding the lower substrate 1 and the upper substrate 3 to each other, the sealant 7 is hardened to complete an LCD device.
In the liquid crystal dispensing method described with above with reference to FIGS. 1A, 1B, and 1C, liquid crystal is directly dispensed onto the substrate. The direct dispensing method can decrease the process time for forming the liquid crystal layer compared to liquid crystal injection methods because the lengthy process for injecting liquid crystal is avoided.
However, the related art liquid crystal dispensing method has the following disadvantages.
In the liquid crystal dispensing method of the related art, since the sealant 7 has no inlet, the sealant pattern may be changed due to external pressure applied when performing a bonding process.
In case of the liquid crystal injection method, the sealant pattern has an inlet. Thus, even though the external pressure is applied to the substrates on performing a bonding process, it is possible to decrease the impact of external pressure. However, since the liquid crystal dispensing method of the related art uses a sealant having no inlet, the sealant pattern may be deformed when performing the bonding process.